Wind turbine generator systems generating electricity using wind power, which is natural energy, have been conventionally known. This type of wind turbine generator system includes a rotor head to which wind turbine blades are attached, a main shaft coupled to the rotor head so as to integrally rotate with the rotor head, a gear box coupled to the main shaft that rotates by means of wind power received by the wind turbine blades, and a generator driven by a shaft output from the gear box, which are provided in a nacelle mounted atop a tower. In the thus configured wind turbine generator system, the rotation of the main shaft and the rotor head provided with the wind turbine blades that convert wind power to rotary power generates shaft output. The output of the shaft whose rotational speed is stepped-up by the gear box coupled to the main shaft is transmitted to the generator. Accordingly, the shaft output obtained by converting wind power to rotary power works as the driving source of the generator, and thereby electricity can be generated using wind power as the motive energy of the generator.
The above-described known wind turbine generator system automatically starts or stops in response to a signal of a wind speed value measured with an anemometer.
In particular, when wind is strong such that the wind speed value is a certain level or more, cut-out control where the electricity generation is stopped by changing the pitch angles of the wind turbine blades is carried out to protect the system (for example, see Patent Document 1).
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2004-84527